Drainage bags are commonly used for individuals who have undergone abdominal surgery involving a colostomy, ileostomy, ureterostomy or the like. Such surgical procedures necessitate the diversion of a bowel or urinary duct through a stoma formed in the individual's abdominal wall, whereby liquids and other waste materials may be discharged from the body through the stoma. The drainage bags are applied to the body of the individual so as to communicate with the stoma for receiving the liquids and waste materials expelled therefrom. Inasmuch as the discharges from the stoma are usually involuntary, the drainage bags are generally worn continuously, except when they are being replaced by another such bag.
Drainage bags are also useful for receiving urine from individuals who have ailments which impair their ability to control the release of urine. If the individuals are not bedridden, the bags are typically worn while the individual moves about from place to place.
All of the drainage bags described above suffer from a common problem. This problem involves the backflow of liquid in the bag as the individual moves about. Such backflow causes an unsanitary condition and, in addition, can cause the individual discomfort resulting from skin irritation and possibly infection.
In the past, there have been various attempts to overcome the backflow problem associated with drainage bags by providing the bags with one-way flap valves designed to permit liquid flow in one direction but not in an opposite direction. Such one-way valves are disclosed, for instance, in U.S. Pat. Nos. 4,084,590; 3,780,739 and 3,618,606. The flap valves disclosed in these patents and all of the other known flap valves for drainage bags require at least two plastic flaps to form the valves. Thus, the prior art flap valves can be rather expensive to manufacture because they require two layers of plastic. Also, the prior art valves are either attached to a catheter tube which extends into the bags between the sides thereof or to the sides of the bags themselves. As the bags with the valves attached to the sides thereof become filled with liquid, they assume a generally cylindrical shape, causing the two side seams of the bags to move closer to each other and, consequently, the flaps, which are normally flat, to become draped or folded. Such draping or folding of the flaps inhibits their proper closing, whereby fluid may pass through the valves in both directions rather than in just one direction.